Manipulate Date in java.

dateAfterMillis.java

/**
 * Returns a {@link Date} corresponding to the given Date plus time passed in milliseconds.
 *
 * @param startingDate The base Date used to get the future Date.
 * @param timePassed   The time (in milliseconds) to be added to the <b>startingDate</b>
 * @return The {@link Date} in the future after <b>timePassed</b> milliseconds from <b>startingDate</b>.
 */
public Date dateAfterMillis(Date startingDate, long timePassed) {
    Date endingDate = new Date();
    endingDate.setTime(startingDate.getTime() + timePassed);

    return endingDate;
}

dateFromString.java

/**
 * Converts given string to date.
 *
 * @param rawDate The string to be converted.
 * @return {@link Date} converted from the given string.
 */
public Date dateFromString(String rawDate) {
    if (rawDate.equals("")) {
        return new Date(); // Will return the current time
    }

    SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'", Locale.US);
    format.setTimeZone(TimeZone.getTimeZone("UTC"));
    Date date = new Date();

    try {
        date = format.parse(rawDate);
    } catch (ParseException e) {
        Log.e(TAG, "Could not parse the date to format");
    }

    return date;
}

dateToLocalTimeZone.java

/**
 * Converts the given date to local timezone in the format "hh:mm a".
 *
 * @param date The {@link Date} to be converted.
 * @return A {@link String} in the format "hh:mm a" for the converted date.
 */
public String dateToLocalTimeZone(Date date) {
    SimpleDateFormat format = new SimpleDateFormat("hh:mm a", Locale.getDefault());
    format.setTimeZone(TimeZone.getDefault());

    return format.format(date);
}

millisLeftToDate.java

/**
 * Returns how many milliseconds are left to reach the given date.
 *
 * @param endDate {@link Date} to calculate how many milliseconds are left to get to it.
 * @return The time left, in milliseconds, to get to the given date.
 */
public long millisLeftToDate(Date endDate) {
    return endDate.getTime() - (new Date()).getTime();
}

stringFromDate.java

/**
 * Converts given date to a string.
 *
 * @param date The date to be converted.
 * @return {@link String} converted from the given date.
 */
public String stringFromDate(Date date) {
    SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'", Locale.US);
    format.setTimeZone(TimeZone.getTimeZone("UTC"));

    String dateString;
    dateString = format.format(date);

    return dateString;
}

timeSinceDate.java

/**
 * Returns the time passed since given date.
 *
 * @param pastDate The basis {@link Date} from the past.
 * @return A {@link String} in the format "H:MM:SS" or "MM:SS" corresponding to the time passed.
 */
public String timeSinceDate(Date pastDate) {
    long timePassed = (new Date()).getTime() - pastDate.getTime();

    return DateUtils.formatElapsedTime(timePassed / 1000);
}